Metal depositions from alkoxides



United States Patent 3,216,845 METAL DEPOSITIONS FROM ALKOXIDES James C.Brown, Cleveland, Ohio, assignor to Fer-r0 Corporation, Cleveland, Ohio,a corporation of Uhio N0 Drawing. Filed Sept. 6, 1962, Ser. No. 221,86217 Claims. (Cl. 11735) The present invention relates to methods ofdepositing an elemental metal from an alkoxide of the metal and analcohol.

While the gradual heating of a metal salt of an orgamc acid or a metalalkoxide, when the metal is more electropositive than hydrogen,generally leads to thermal decomposition, with the formation of themetal oxide or carbonate, the present invention provides for a methodfor obtaining directly in elemental form such metals as nickel orcobalt, from suitably chosen alkoxides, by moderate heating, withoutapparent formation of the metal oxide or carbonate.

It is an object of the present invention to provide a method ofdepositing a metal from an alkoxide thereof.

It is an object of the present invention to provide a method ofobtaining a metal in elemental form from a compound thereof by splittingthe metal-oxygen bond of a metal alkoxide in which the metal is one ofthe electromotive series that is above hydrogen and below llOIl.

It is an object of the present invention to provide a method ofdepositing a metal such as nickel in the form of a continuous metalmirror on a substrate such as glass by heating a metal alkoxide such asnickel alkoxide of ethylene glycol at a relatively low temperature, say,of at least about 200 C. to deposit the nickel therefrom.

These and other objects will be apparent from the specification thatfollows and the appended claims.

The present invention provides a convenient inexpensive method ofdepositing a metal such as nickel on a substrate such as glass, metal,or a ceramic base by heating a metal alkoxide such as nickel alkoxide ofethylene glycol at a relatively low temperature, say preferably about200 C., to break the nickel-oxide bond homolytlcally and deposit thenickel in a powdery film or mirrorlike film on the substrate.

The metals that can be deposited as above described from theirrespective alkoxides are nickel, cobalt, cadmium, tin and lead. Thesemetals are all listed in the electromotive series above hydrogen andbelow iron. See Langes Handbook of Chemistry, Ninth Edition, pages12l21218.

Metal alkoxides of more electropositive metals such as iron, zinc,manganese and chromium are not suitable in accordance with the presentinvention to obtain a deposit of powder or a metallic film.

Although it is not completely understood and applicant does not wish tobe strictly held to his theory, it is believed that ordinarily difiicultto break metal-oxygen bond can be broken in the particular alkoxideshereinafter described because the organic portion of the alkoxidemolecule, by virtue of chelation or intramolecular coordinate bonding ofthe metal atom to a sulfur, nitrogen, or oxygen atom other than that ofthe alkoxide linkage, reduces the energy required to sever homolyticallythe bond between the metal and the alkoxide oxygen. This reduction inenergy is snfficient to make Possible the thermal deposition of metalsless electropositive than iron. When metals more electropositive thaniron are used, their bond energies are presumably similarly aflFected,but the energy requirements remain too high for such reduction. Formetals below hydrogen in the electromotive series, the energyrequirements for forma tion of the metal are sufficiently low that theymay in some cases form metal on heating even if the modification of theenergy requirement by chelation or coordinate bonding is non-existent.Thus, this invention is most clearly demonstrable in a range ofcompositions where no other known mechanism suffices to explain thereactions.

Suitable alkoxides of cadmium, cobalt, nickel, tin and lead can beprepared as described in copending application Serial No. 64,705, filedOctober 25, 1960, now abandoned, of Charles H. Fuchsman and assigned tothe same assignee as the present application' As therein disclosed, thepreferred alcohols for preparing the alkoxides are polyfunctionalalcohols having a functional group such as an oxygen atom or a sulfuratom at a position alpha or beta to the carbon atom carrying thehydroxyl group that enters into the hydrocarbon reaction. Alcoholshaving the above structure and exemplified by glycols such as ethyleneglycol, thiodiethanol and 1,3-propylene glycol.

In accordance with the above description of the preferred polyfunctionalalcohol, suitable alcohols are those having the general formula:

511 wherein R is alkyl, aryl, alkaryl, aralkyl, cycloalkyl,alkoxylalkyl, alkoxyaryl, aroxyalkyl, aroxyaryl, alkoxycycloalkyl,cycloalkoxyalkyl, hydroxyalkyl, hydroxycycloalkyl, andhydroxyalkoxyalkyl; X is oxygen or sulfur, R" is hydrogen or one of theradicals listed for R, and n is 1 or 2.

While primary alcohols are preferred, secondary alcohols may also beuse-d as indicated below in the specific examples. Thus, R" in Formula Imay be hydrogen, or an alkyl group, such as methyl, ethyl, propyl,isopropyl, butyl, t-butyl, amyl, t-amyl, hexyl, cyclohexyl, 2-ethylhexyl, nonyl, decyl, dodecyl, lauryl, cetyl, and octadecyl; or, thesealkyl groups may contain oxygen attached to two carbon atoms or to asingle carbon atom. In the latter case, the oxygen may be singly bondedto such carbon atom as hydroxyl. The radical R includes the sameradicals as mentioned above as useful for R with the exception ofhydrogen, and additionally aryl radicals such as phenyl and naphthyl;alkaryl radicals such as cresyl, xylyl, mesityl, p-ethylphenyl,p-t-butylphenyl, p-Z-ethylhexylphenyl, p-l,1,3,3-tetramethylbutylphenyl,p-dodecylphenyl; aralkyl radicals such as benzyl, phenylethyl,phenylcyclohexyl; cycloalkyl radicals such as cyclohexyl, cyclopentyl,methylcyclohexyl; alkoxyalkyl radicals, such as methoxy ethyl,ethoxymethyl, ethoxyethyl, propoxyethyl; alkoxyaryl radicals such asmethoxyphenyl, ethoxyphenyl; aroxyalkyl radicals such as phenoxymethyl,phenoxyethyl, phenoxypropyl; aroxyaryl radicals such as phenoxyphenyl;alkoxycycloalkyl radicals, such as methoxycyclohexyl, ethoxycyclohexyl;cycloalkoxyalkyl radicals, such as cyclohexoxymethyl, cyclohexoxyethyl;hydroxyalkyl radicals such as hydroxymethyl, hydroxyethyl,hydroxypropyl, hydroxybutyl, hydroxyoctyl; hydroxycycloalkyls, such asp-hydroxycyclo- \hexyl; and hydroxyalkoxy alkyl radicals such ashydroxyethoxyethyl, hydroxypolyethoxyethyl.

Also suitable as the alcohol component of the metal alkoxides oralcoholates is an alcohol having 8 to 28 carbon atoms and having a fattyacid residue of at least 8 carbon atoms in its molecular chain such asthe fatty acid-imidazoline condensation product having the generalformula:

where n is 6 to 12.

Also suitable is the imidazoline reaction product of oleic acid-such amaterial being sold commercially as Amide O by Geigy IndustrialChemicals, a Division of Geigy Chemical Corporation, Yonkers, New York.

One of the preferred alkoxides of the present invention is one formedfrom a cyclic ether-alcohol material having a cyclic configuration inwhich the hydroxyl group is attached to a carbon atom beta to the etheroxygen atom of the cyclic structure. Suitable cyclic ether-alcoholmaterials, preferably having about to 7 carbon atoms, aretetrahydrofurfuryl alcohol and tetrahydropyrane-2- methanol.

Also suitable as the alcohol component of the alkoxides are aminoalcohols preferably having about 4 to 8 carbon atoms and having ahydroxyl group in a position beta to the amino nitrogen atom. Suitableamino alcohols are diethyl aminoethanol and dimethylaminoethanol.

In general, the metal alkoxide starting materials of the presentinvention are produced by reacting (1) a divalent salt of a carboxylicacid (preferably acetic acid) and a suitable metal such as nickel and(2) an alcohol as previously described and thereafter removing themonocarboxylic acid formed such as acetic acid by distillation oranother suitable means. Inasmuch as the boiling point of acetic acid atatmospheric pressure is relatively low, being about 118 C. and inasmuchas the acid is generally diluted, generally the reaction temperatureemployed in preparing the alkoxides is about 130 C. up to as high asabout 158 to 168 C.

The reactions may be conducted in a solvent; or where the alcohol isliquid at the reaction temperature, an excess of alcohol may be used asthe solvent. The reaction may be conducted at atmospheric pressure orunder vacuum and the temperature may range from room temperature to thetemperature at which the carboxylic acid produced in the course of thereaction volatilizes under the conditions of pressure employed.

In general, suitable carboxylic acids that can be used to prepare themetal alkoxide starting material are: propionic, butyric, isooctoic,Z-ethylbutanoic, cyclohexane carboxylic, acrylic, 3-(2-ethylbutoxy)propionic acid in which the acid preferably has about 2 to 8 carbonatoms. but less volatile acids containing greater numbers of carbonatoms (e.g., naphthenic acids of acid value of about 300) can be used,but more extreme conditions, particularly of vacuum, may be required toconduct the necessary reaction.

The following examples are intended to illustrate the present inventionand not to limit the same in any way:

Exan zple 1 This example illustrates the deposition of nickel from analkoxide of nickel and a beta-hydroxy ethyl derivative of a coconutfatty acid-imidazoline condensation product.

The nickel alkoxide starting material was previously prepared byreacting nickel acetate with the above described alcohol, which alcoholhad the following general formula prior to reaction with the nickelacetate to form the resultant nickel alkoxide:

where n is an integer from 6 to 12.

The above nickel alkoxide material was placed in a 25 x mm. test tubeequipped with a glass stirrer and heated with stirring by mechanicalmeans at a temperature of about 250 C., in 50 minutes a powdery film ofnickel appeared. After about 5 hours of heating, the powdery film becamea continuous metal mirror deposited on the inner glass surface of thetest tube. The identity of the mirror material as nickel was confirmedby X-ray analysis and by qualitative chemical analysis.

Example 2 A bright nickel mirror was deposited on a glass substrate,which was the inner wall of a test tube, by heating in the test tube thenickel alkoxide of Example 1 in accordance with the methods describedtherein, except that an equal amount of nonyl phenol was used to dilutethe nickel alkoxide. A powdery metal deposit of nickel appeared in 45minutes and the formation of a nickel mirror from the powdery depositoccurred in three hours.

Example 3 The nickel alkoxide of an alcohol that is the beta hydroxyethyl derivative of oleic acid-imidazoline condensation product washeated at 205 C. for about 30 minutes as in Example 1 to provide apowdery nickel film. Continued heating for about a total time of about 2/2 hours produced a mirror-like deposit.

Example 4 An equal mixture of nonyl phenol and the nickel alkoxide ofExample 3 was heated at 205 C. to deposit nickel therefrom. The time forfirst film formation and the time for mirror formation was about thesame as reported in Example 3.

Example 5 Nickel alkoxide of nonyl phenoxy ethanol was prepared byheating about equal molar amounts of nickel acetate tetrahydrate andnonyl phenoxy ethanol in xylene under reflux for about 3 to 4 hours andthe reaction mixture filtered to obtain a dark green solution as thefiltrate in a manner similar to that described and claimed in thepreviously described copending application of Charles H. Fuchsman.

The dark green solution was stripped of solvent, and the solution heatedto slowly form a nearly white solid material of paste-like consistency.On continued heating, the paste-like mass became fluid again and darkgreen in color. Heating was continued at 205 C. and the sys tem heldunder aspirator vacuum to remove acetic acid.

Upon continued heating at 205 C., a mirror-like deposit of nickel wasobtained on the inner glass wall of the reaction vessel. A portion ofthe nickel apparently was deposited at about 205 C. as a mirror evenbefore all the nickel had been converted to the nickel alkoxide.

Example 6 During preparation of the Ni alcoholate of diethylene glycolmono-n-butyl ether (commercially available as Dowanol-19), the fine miston the upper flask wall (at 245-250) deposited a nickel mirror whileonly 25% of the Ni had been converted to alcoholate.

Example 7 Using the following solid derivatives of \gl ycol s, 1.0 g. ofsolid was suspended in g. of mineral oil (Nujol) in a ml. test tube andheated in an oil bath at 205- -5 C. without agitation:

A lead mirror was deposited from a lead alkoxide dissolved in mineraloil having a boiling point over about 370 C. The alkoxide used was thelead alkoxide of the beta-hydroxy ethyl derivative of a coconut fattyacidimidazoline condensation product, this particular alcohol beingdescribed in Example 1 and being sold commercially by Geigy Chemical asAmine C. The temperature employed in depositing the lead was 205 C. andthe time was about one hour.

In the above examples, cadmium, cobalt, nickel, tin and lead may besubstituted in whole or part for the metal actually used to obtainnearly equivalent results and, thus, to provide at least some of thebenefits of the present invention. Of these metals, as previouslyindicated, nickel and cobalt are highly preferred. Also, in the aboveexamples, as previously indicated, other alkoxides or alcohols can beused to produce the metal powder, the powdery film or the mirror-likefilm. For instance, alcohols that can be substituted for the alcoholsactually employed to provide substantially equivalent results are thefollowing: tetrahydrofurfuryl alcohol, ethylthioethanol,triethanolamine, trimethylolpropane, pentaerythritol dicaprate,1,3-propane diol, ethoxytriglycol, propylene glycol, ethylene glycolmono methyl ether, ethylene glycol mono-n-hexyl ether, N,N-diethylaminoethanol.

Also in addition to the above preferred alcohols, metal alkoxides of thepolyfunctional alcohols having a functional group alpha or beta to thehydroxyl group (as previously described herein) can be substituted forthe particular metal alkoxide used in the examples to provide at leastsome weakness of the metal-oxygen bond and the subsequent deposit of themetal.

Although the exact temperature employed to break the metal-oxygen bondof the metal alkoxide may vary somewhat depending upon the alcohol and,in some cases, the metal salt originally used to produce the alkoxide asfor instance when the nickel alkoxide is produced by the reaction ofnickel acetate and ethylene glycol and the reaction product heatedwithout removing the same from the reaction vessel or further purifyingor treating the same, generally a temperature of at least about 180 C.should be employed to break the above described metal-oxygenparticularly in the case of metals such as nickel and cobalt that arehigher in the electromotive series than a metal such as lead.Preferably, the decomposition temperature used should be at least about200 C. and generally the best results are obtained at about 200 to 220C., although occasionally such as described in Example 6, a temperatureof 245250 C. or higher say, about 270 C., may be required to obtain ametallic mirror or even an elemental metal powder.

It is also apparent that modifications of the invention may be madewithout changing the spirit thereof, and it is intended that theinvention be limited only by the appended claims.

What is claimed is:

1. A method comprising the steps of heating a metal alkoxide of (A) ametal that is in the electromotive series between iron and hydrogen, and-(B) an alcohol to a temperature of at least about C. and sufficient todeposit said metal from said alkoxide on a substrate, the alcohol beingselected from a member of the group consisting of (1) an alcohol havingabout 8 to 28 carbon atoms and having a residue of a fatty acid in itsmolecular chain of at least 8 carbon atoms, (2) a polyfunctional alcoholhaving the general formula:

wherein R is a radical selected from the group consisting of alkyl,aryl, alkaryl, aralkyl, cycloalkyl, alkoxyalkyl, alkoxyaryl, aroxyalkyl,alkoxycycloalkyl, cycloalkoxyalkyl, hydroxyalkyl, hydroxycycloalkyl andhydroxyalkoxyalkyl; X is selected from the group consisting of oxygenand sulfur, R is selected from the group consisting of hydrogen and Rradicals; and n is an integer from 1 to 2, (3) a polyfunctional alcoholhaving the general formula:

wherein R" is selected from a member of the group consisting of hydrogenand R radicals and n is an integer from 1 to 2, (4) a cyclicether-alcohol compound having a cyclic structure including an etheroxygen atom and a hydroxyl group attached to a carbon atom in a positionbeta to said ether oxygen atom, and (5) an organic amino alcohol havinga hydroxyl group attached to a carbon atom in a position beta to theamino nitrogen atom.

2. A method of obtaining an elemental nickel from a nickel alkoxidecomprising the step of heating to a temperature of about 180 to 270 C.to deposit nickel on a substrate, a nickel alkoxide of an alcohol of thegroup consisting of (1) an alcohol having about 8 to 28 carbon atoms andincluding a fatty acid residue of at least 8 carbon atoms in itsmolecular chain (2) a polyfunctional alcohol having the general formula:

wherein R is a radical selected from the group consisting of alkyl,aryl, alkaryl, aralkyl, cycloalkyl, alkoxyalkyl, alkoxyaryl, aroxyalkyl,alkoxycycloalkyl, cycloalkoxyalkyl, hydroxyalkyl, hydroxycycloalkyl andhydroxyalkoxyalkyl; X is selected from the group consisting of oxygenand sulfur, R is selected from the group consisting of hydrogen and Rradicals; and n is an integer from 1 to 2, (3) a polyfunctional alcoholhaving the general formula:

wherein R is selected from a member of the group consisting of hydrogenand R radicals and n is an integer from 1 to 2, (4) a cyclicether-alcohol compound having a cyclic structure including an etheroxygen atom and a hydroxyl group attached to a carbon atom in a positionbeta to said ether oxygen atom, and (5) an organic amino alcohol havinga hydroxyl group attached to a carbon atom in a position beta to theamino nitrogen atom.

3. A method of depositing metal from an alkoxide on a substrate, themethod comprising heating a metal a'lkoxide of a metal that is one ofthe electromotive series above hydrogen and below iron and apolyfunctional alcohol to a temperature of at least about 200 C. andsulficient to deposit said metal on a substrate, said alcohol having thegeneral formula:

wherein R is a radical selected from the group consisting of alkyl,aryl, alkaryl, aralkyl, cycloalkyl, alkoxyalkyl, alkoxyaryl, aroxyalkyl,alkoxycycloalkyl, cycloalkoxyalkyl, hydroxyalkyl, hydroxycycloalkyl andhydroxyalkoxyalkyl; X is selected from the group consisting of oxygenand sulfur, R" is selected from the group consisting of hydrogen and Rradicals; and n is an integer from 1 to 2.

4. A method of depositing a metal that is one of the el ctromotiveseries above hydrogen and below iron from an alkoxide on a substratecomprising heating to a temperature of about 180 to 270 C., the metalalkoxide of said metal and a polyfunctional alcohol having the generalformula:

wherein R is a radical selected from the group consisting of alkyl,aryl, alkaryl, aralkyl, cycloalkyl, alkoxyalkyl, alkoxyaryl, aroxyalkyl,alkoxycycloalkyl, cycloalkoxyalkyl, hydroxyalkyl, hydroxycycloalkyl andhydroxyalkoxyalkyl; X is selected from the group consisting of oxygenand sulfur; R is selected from the group consisting of hydrogen and Rradicals; and n is an integer from 1 to 2.

5. A method of depositing nickel from a nickel alkoxide comprisingheating to a temperature of at least about 200 C. and sufiicient todeposit nickel on a substrate, a nickel alkoxide of an alcohol havingthe general formula:

wherein R is a radical selected from the group consisting of alkyl,aryl, alkaryl, aralkyl, cycloalkyl, alkoxyalkyl, alkoxyaryl, aroxyalkyl,alkoxycycloalkyl, cycloalkoxyalkyl, hydroxyalkyl, hydroxycycloalkyl andhydroxyalkoxyalkyl; X is selected from the group consisting of oxygenand sulfur, R" is selected from the group consisting of hydrogen and Rradicals; and n is an integer from 1 to 2.

6. A method of depositing metal as defined in claim 1 in which saidmetal is cobalt.

7. A method of depositing metal as defined in claim 1 in which saidmetal is cadmium.

8. A method of depositing metal as defined in claim 1, in which saidmetal is tin.

9. A method of depositing nickel on a glass substrate comprising thesteps of heating to a temperature of about 200 to 220 C. a nickelalkoxide of ethylene glycol suspended in a diluent comprising mineraloil.

10. A method of depositing cobalt on a substrate comprising the step ofheating to about 200 to 220 C. a cobalt alkoxide of ethylene glycol toprovide on the substrate a continuous metal mirror of cobalt.

11. A method of obtaining metallic cobalt from a cobalt alkoxidecomprising the step of heating cobalt alkoxide of thiodiethanolsuspended in mineral oil to a temperature of about 200 to 220 C. todeposit cobalt on a substrate.

12. A method of obtaining a deposit of metallic cadmium from a cadmiumalkoxide comprising heating cadmium alkoxide of ethylene glycolsuspended in mineral oil to a temperature of about 200 to 220 C. tothereby deposit metallic cadmium on a substrate.

13. A method comprising the step of heating a metal alkoxide of (A) ametal that is one of the elements in the electromotive series betweenhydrogen and iron and (B) tetrahydrofurfuryl alcohol to a temperature ofat least about 180 C. and sufficient to deposit said metal on asubstrate.

14. A method comprising the step of heating a metal alkoxide of (A) ametal that is one of the elements in the electromotive series betweenhydrogen and iron and (B) tetrahydropyrane-Z-methanol to a temperatureof at least about 180 C. and sufiicient to deposit said metal on asubstrate.

15. A method comprising the step of heating a metal alkoxide of (A) ametal that is one of the elements in the electromotive series betweenhydrogen and iron and (B) an organic amino alcohol containing from 4 to8 carbon atoms and having a hydroxyl group attached to a carbon atomthat is in a position beta with respect to the amino nitrogen atom to atemperature of at least about 180 C. and sufiicient to deposit saidmetal on a substrate.

16. A method of depositing nickel on a substrate comprising heating atabout 200 to 220 C. a nickel alkoxide of an alcohol having the generalformula:

N UH: H3C (CH2)11 (1112 N (JH OH OH where n is 6 to 17, to produce apowdery film of nickel, and thereafter heating the powdery film toprovide a continuous metal mirror of nickel.

17. A method of depositing nickel on a substrate in a continuous metalmirror comprising heating at about 200 to 220 C. a nickel alkoxide of analcohol of a betaethanol derivative of an oleic acid-imidazolinecondensation product.

References Cited by the Examiner UNITED STATES PATENTS 9/50 Young117-113 X 6/62 Berger 117160 X

1. A METHOD COMPRISING THE STEPS OF HEATING A METAL ALKOXIDE OF (A) AMETAL THAT IS IN THE ELECTROMOTIVE SERIES BETWEEN IRON AND HYDROGEN, AND(B) AN ALCOHOL TO A TEMPERATURE OF AT LEAST ABOUT 180*C. AND SUFFICIENTTO DEPOSITE SAID METAL FROM SAID ALKOXIDE ON A SUBSTRATE, THE ALCOHOLBEING SELECTED FROM A MEMBER OF THE GROUP CONSISTING OF (1) AN ALCOHOLHAVING ABOUT 8 TO 28 CARBON ATOMS AND HAVING A RESIDUE OF A FATTY ACIDIN ITS MOLECULAR CHAIN OF AT LEAST 8 CARBON ATOMS, (2) A POLYFUNCTIONALALCOHOL HAVING THE GENERAL FORMULA: